It is important to be able to measure and evaluate the performance of a telecommunications system both generally from the overall system perspective and in more detail from the perspective of specific telecommunications equipment. The present invention is particularly directed to the issue of determining how often a telecommunications path, used by a subscriber to request and receive a telecommunications service from a telecommunications system, is "down" as a result of some type of fault or failure in the subscriber path or in the communications system itself. One example of a subscriber path is a wireline which connects a subscriber device such as a telephone to a local telephone exchange. Since a subscriber wireline is perhaps the simplest and most common example of a subscriber path, it is used in the subsequent description for purposes of illustration but not limitation.
One way to address this issue might be to manually sample the status of the subscriber lines, collect and correlate the manually obtained data, and then calculate various statistical parameters based on those collected figures. But a manual approach is tedious, time consuming, expensive, and not altogether effective because of these limitations. Another approach might be simply to measure the amount of time that a telecommunications center such as a local exchange, is down or "out-of-order" and use that as a general measure of how often subscriber lines are down. However, this latter approach is too general and does not account for fault or other blocking events that effect the operational status of the subscriber lines independent of the telecommunications center operation/operability.
It is therefore an object of the present invention to provide a technique that automatically monitors the operational status of individual subscriber lines to determine how often a subscriber line on average and/or individually is blocked or down so that it cannot be used by a subscriber device to receive or request communication services.
It is a further object of the present invention to provide a subscriber line down time monitoring and calculation technique that accounts for causes in subscriber line down time attributable to multiple sources including subscriber line hardware, software specifically controlling the subscriber line hardware, and other external sources including any widespread system down time of the telecommunications center to which the subscriber line is connected.
It is a further object of the present invention to provide such measurement and calculation parameters simply, inexpensively, and with little data processing overhead using existing resources in conventional telecommunications systems.
The method of the present invention monitors the operation of communications equipment including plural subscriber communications paths used by corresponding subscriber devices to receive information from or transmit information to a telecommunications center such as a local telephone exchange. One or more data records is maintained in computer memory for each subscriber path connected to the communications center. Each data record is updated using recently determined data relating to the operational status of each subscriber path. A computer then determines from the updated records a subscriber path blocking parameter. A blocked subscriber path means that the subscriber path cannot be used as intended as a communications path.
The subscriber path blocking parameter may represent the amount of time that a subscriber path is blocked, such as an average amount of time each subscriber path is blocked, or an amount of time that an individual one of the subscriber paths is blocked. The average amount of blocked time per subscriber line for a particular time period is sometimes referred to as line down time (LDT) if the blocking fulfills certain "line down" criteria. It should be understood, however, that the "line down" time calculation also applies to more sophisticated subscriber paths that might also include for example a time division multiplexed time slot. Even if a subscriber path is blocked, it may not be treated as "down" or "operational" unless it satisfies one or more predetermined "line down" criteria. One example criterion is an amount of time that a subscriber path must be blocked (faulty) or unblocked (in operation), e.g., 30 seconds, before that subscriber path will be treated as "down" or "operational," respectively.
Another advantageous feature of the present invention is that the communications center itself, such as the local telephone exchange, is monitored to determine the amount of time (if any) that it is not providing service to the subscriber devices. The system's operational status is monitored in addition to the operational status of the subscriber paths which connect the subscriber devices to the communications system. The amount of time that the subscriber paths are detected as "down" for any reason is calculated based both on the detected operational status of each individual subscriber path and on the determined amount of time that the communications system is not operational.
In a particular embodiment of the present invention that includes a telecommunications center including a switching node, telecommunications subscriber devices, and subscriber lines used by corresponding ones of the subscriber devices to obtain a communications service from the telecommunications center, electronic circuitry detects and reports faults related to each subscriber line. Reported faults are used to determine if the subscriber line should be blocked. The subscriber line blocking state (operational status) is used to determine if the subscriber line is "down" or "operational" according to the line down criteria. A data processor evaluates whether any subscriber line has recently been blocked and whether any subscriber line has recently become unblocked. Subscriber line records stored in memory are updated based on the detected operational status for each subscriber line.
A line interface circuit is connected between a corresponding subscriber line and the telecommunications center. Each line interface circuit includes circuitry that monitors faults of the corresponding subscriber line which could affect whether the corresponding line is blocked. Such line interface circuits may be located at the telecommunications center or at an intervening access node.
In a preferred example embodiment, a plurality of counters may be used in performing line down time calculations. A first counter counts a number of subscriber lines currently detected as down based on the detected operational (blocking) status of the subscriber lines. A second counter accumulates an accumulated number of lines down using periodically obtained values from the first counter. The data processor calculates an average amount of time each subscriber line is down using a value obtained from the second counter and a total number of fully-connected subscriber lines. A fully-connected subscriber line is a line which has been assigned to provide service to a particular subscriber device and has been connected and/or activated so that it is capable of providing that service. The fact that a subscriber line is fully-connected or otherwise activated does not mean that it is necessarily operational or non-operational. A third counter counts a number of currently fully-connected subscriber lines. A fourth counter maintains an accumulated number of fully-connected subscriber lines using periodically obtained values from the third counter.
By using software variables and counters, the preferred example embodiment of the present invention provides a comprehensive and detailed measurement of subscriber line down time useful in evaluating performance. The features and advantages of the present invention will be described in further detail below in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a function block diagram showing one example application of the present invention using one or more PSTN line connections to a local exchange;
FIG. 2 is a function block diagram showing another example application of the present invention using one or more PSTN connections to a local exchange via a PCM (Pulse Code Modulation) connected Access Node (AN);
FIG. 3 is a flowchart diagram illustrating a method in accordance with the present invention;
FIG. 4 is a function block diagram showing hardware and software data structures used in implementing the preferred example embodiment of the present invention; and
FIGS. 5-7 are flowchart diagrams that illustrate procedures employed in implementing the preferred example embodiment of the present invention.